Scientists cut whiskers off rats to learn more about how the rodents hunt

From cats to rats, many animals follow the wind to find food and a mate, as well as avoiding predators, but exactly how they do this had remained a mystery.

Now, researchers have found these animals likely use their whiskers for each of these tasks.

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Experts at the University of Northwestern’s McCormick School of Engineering set up an experiment to test the abilities of rats’ whiskers, comprising five equally-spaced fans arranged in a semicircle on a specially-made six-foot table.

In each trial, one of the five fans was randomly selected to blow air towards a “start-door” holding a rat, located on the opposite side of the table. The rat was tasked with running from the door towards the fan blowing air, and go down a rat-sized hole directly in front of it.

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Each of the five holes led to a tunnel beneath the table, where the rat was rewarded for choosing the correct fan. Cameras positioned above the table recorded the rats’ performance.

With five fans on the table, the rats could perform at 20 per cent just by chance, but learnt how to gain rewards. This led them to choose the right burrow 60 per cent of the time or more, for 10 days in a row.

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After this, the researchers cut off the rats’ whiskers – a painless procedure - and looked for changes in their behaviour. They found the rodents’ performance dropped by 20 per cent.

This indicates the rats chose to use their whiskers to follow the wind and find food above other sensory cues.

“We didn’t require the rats to use their whiskers for this task,” PhD student and co-author of the study, Yan Yu explained.

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“They could use many other sources of information, including movement of the fur, mechanical cues from the skin, or thermal cues from the eyes, ears, or the snout.”

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The use of multiple cues explains why rats were still able to perform above-chance levels after whisker removal, while the drop in performance suggests whiskers play a big part in detecting the source of wind.

Chris Bresee, another PhD student and study author said: “Rats still choose to rely heavily on their whiskers, which suggests that whiskers facilitate wind-sensing even when wild rats explore naturally.”

The experiment, described in the journal Science Advances, took place in a dark room with extra ambient noise to make sure the animals weren’t simply reacting to the noise or sight of a spinning fan. Another group of rats was trained to run towards light instead of a fan – and the results were very similar.

The researchers are now investigating the mechanical and neural signals that underlie rat’s ability to do the task. They hope this information will enable them to construct artificial flow sensors that can be used on robots to follow the wind.

In an earlier experiment, published in the journal of Experimental Biology, the researchers found whiskers bend in the direction of the wind — and the harder the wind blows, the more the whiskers bend and vibrate.

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“When the whisker bends, it presses on receptors at the whisker’s base” PhD student and co-author Matthew Graff said. “Our behavioural work now suggests that this mechanical information is actually used by the rat to locate an airflow source.”

While the team has only studied the phenomenon in rats, they believe cats and dogs both use their whiskers in a similar way, because their whiskers are arranged in a very similar way.

Yu added: “It would make sense for all sorts of animals to exploit this mechanical information, given that sensing wind direction is important for so many behaviours.”